Information Notice 2005-14, Fire Protection Findings on Loss of Seal Cooling to Westinghouse Reactor Coolant Pumps: Difference between revisions

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{{#Wiki_filter:UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555-0001 June 1, 2005 NRC INFORMATION NOTICE 2005-14:FIRE PROTECTION FINDINGS ON LOSS OFSEAL COOLING TO WESTINGHOUSE
{{#Wiki_filter:UNITED STATES


===REACTOR COOLANT PUMPS===
NUCLEAR REGULATORY COMMISSION
 
OFFICE OF NUCLEAR REACTOR REGULATION
 
WASHINGTON, D.C. 20555-0001 June 1, 2005 NRC INFORMATION NOTICE 2005-14:                  FIRE PROTECTION FINDINGS ON LOSS OF
 
SEAL COOLING TO WESTINGHOUSE
 
REACTOR COOLANT PUMPS


==ADDRESSEES==
==ADDRESSEES==
All holders of operating licenses for pressurized water reactors, except those who havepermanently ceased operations and have certified that fuel has been permanently removed
All holders of operating licenses for pressurized water reactors, except those who have
 
permanently ceased operations and have certified that fuel has been permanently removed


from the reactor vessel.
from the reactor vessel.


==PURPOSE==
==PURPOSE==
The U.S. Nuclear Regulatory Commission is issuing this information notice (IN) to informaddressees about recent inspection findings on post-fire procedural requirements related to
The U.S. Nuclear Regulatory Commission is issuing this information notice (IN) to inform
 
addressees about recent inspection findings on post-fire procedural requirements related to


loss of cooling to reactor coolant pump (RCP) seals. NRC anticipates that recipients will review
loss of cooling to reactor coolant pump (RCP) seals. NRC anticipates that recipients will review


the information for applicability to their facilities and consider taking actions, as appropriate, toavoid similar issues. However, no specific action or written response is required.
the information for applicability to their facilities and consider taking actions, as appropriate, to
 
avoid similar issues. However, no specific action or written response is required.


==BACKGROUND==
==BACKGROUND==
Assuming a fire results in loss of cooling to the RCP seals, licensees may comply with 10 CFRPart 50, Appendix R, "Fire Protection Program for Nuclear Power Facilities Operating Prior toJanuary 1, 1979," by protecting the cooling to the seals or by demonstrating that the plant cancope with RCP seal leakoff flow rates. Many licensees have installed RCP seal packages using
Assuming a fire results in loss of cooling to the RCP seals, licensees may comply with 10 CFR
 
Part 50, Appendix R, Fire Protection Program for Nuclear Power Facilities Operating Prior to
 
January 1, 1979, by protecting the cooling to the seals or by demonstrating that the plant can
 
cope with RCP seal leakoff flow rates. Many licensees have installed RCP seal packages using
 
high-temperature O-rings that will not result in uncontrolled leakage from RCP seals for


high-temperature O-rings that will not result in uncontrolled leakage from RCP seals forconditions with loss of all RCP seal cooling. Licensees also ensure adequate makeup
conditions with loss of all RCP seal cooling. Licensees also ensure adequate makeup


capability to compensate for any RCP seal leakoff and maintain reactor coolant system (RCS)inventory according to requirements of Appendix R, Sections III.G.2, III.G.3, and III.L.1 andperformance goals of Appendix R, Section III.L.2. Note that a plant licensed before January 1,1979, must meet the provisions of Appendix R, Section III.G and III.L and a plant licensed afterJanuary 1, 1979, must implement the fire protection provisions of its operating license.
capability to compensate for any RCP seal leakoff and maintain reactor coolant system (RCS)
inventory according to requirements of Appendix R, Sections III.G.2, III.G.3, and III.L.1 and
 
performance goals of Appendix R, Section III.L.2. Note that a plant licensed before January 1,
1979, must meet the provisions of Appendix R, Section III.G and III.L and a plant licensed after
 
January 1, 1979, must implement the fire protection provisions of its operating license.


==DESCRIPTION OF CIRCUMSTANCES==
==DESCRIPTION OF CIRCUMSTANCES==
At Surry, NRC inspectors found that certain postulated fires could result in the loss of cooling tothe RCP seals. The inspectors noted that the RCP seal vendor, Westinghouse, advised thatincreased seal leakage, to around 21 gpm, could occur if seal cooling is lost and not restored
At Surry, NRC inspectors found that certain postulated fires could result in the loss of cooling to
 
the RCP seals. The inspectors noted that the RCP seal vendor, Westinghouse, advised that
 
increased seal leakage, to around 21 gpm, could occur if seal cooling is lost and not restored


before hot RCS fluid reaches the RCP seals. Additionally, the Westinghouse Owners Group
before hot RCS fluid reaches the RCP seals. Additionally, the Westinghouse Owners Group


(WOG) revised their generic emergency response guidelines for the station blackout event to
(WOG) revised their generic emergency response guidelines for the station blackout event to
Line 46: Line 78:
recommend that RCP seal cooling not be restored following a prolonged loss of seal cooling in
recommend that RCP seal cooling not be restored following a prolonged loss of seal cooling in


which the seal temperature exceeds the RCP seal vendor's recommendations. The licensee
which the seal temperature exceeds the RCP seal vendors recommendations. The licensee


incorporated this guidance into its emergency operating procedures for the response to a loss
incorporated this guidance into its emergency operating procedures for the response to a loss
Line 52: Line 84:
of all alternating current (AC) power event but not in its procedures for safe shutdown of the
of all alternating current (AC) power event but not in its procedures for safe shutdown of the


reactor after a fire. Restoration of seal injection after the seals become hot could lead to
reactor after a fire. Restoration of seal injection after the seals become hot could lead to
 
increased leakage beyond the RCS makeup capability needed to satisfy the performance goals


increased leakage beyond the RCS makeup capability needed to satisfy the performance goalsin Appendix R, Section III.L.2 (NRC Inspection Reports 50-280/03-07 and 50-281/03-07). Similar findings were made at other nuclear power plants. At Turkey Point, NRC inspectorsfound that the post-fire procedures did not provide timely operator action to restore seal
in Appendix R, Section III.L.2 (NRC Inspection Reports 50-280/03-07 and 50-281/03-07).
 
Similar findings were made at other nuclear power plants. At Turkey Point, NRC inspectors
 
found that the post-fire procedures did not provide timely operator action to restore seal


injection and could result in increased RCP seal leakage beyond the capacity of equipment
injection and could result in increased RCP seal leakage beyond the capacity of equipment
Line 60: Line 98:
dedicated to achieve and maintain post-fire safe shutdown according to Appendix R, Section
dedicated to achieve and maintain post-fire safe shutdown according to Appendix R, Section


III.G.2 (NRC Inspection Reports 50-250/04-07 and 50-251/04-07). At North Anna, NRCinspectors found, similar to the Surry finding, that certain fires could result in a loss of seal
III.G.2 (NRC Inspection Reports 50-250/04-07 and 50-251/04-07). At North Anna, NRC
 
inspectors found, similar to the Surry finding, that certain fires could result in a loss of seal
 
cooling. Seal cooling could be restored after the seal had heated up, thereby potentially
 
resulting in increased seal leakage beyond the RCS makeup capability required to satisfy


cooling.  Seal cooling could be restored after the seal had heated up, thereby potentiallyresulting in increased seal leakage beyond the RCS makeup capability required to satisfyAppendix R, Section III.L.2 (NRC Inspection Reports 50-338/03-06 and 50-339/03-06). AtSummer, the inspectors were concerned that the licensee's fire emergency procedure did not
Appendix R, Section III.L.2 (NRC Inspection Reports 50-338/03-06 and 50-339/03-06). At
 
Summer, the inspectors were concerned that the licensees fire emergency procedure did not


direct personnel to reestablish seal cooling flow in a timely manner, potentially leading to
direct personnel to reestablish seal cooling flow in a timely manner, potentially leading to


increased seal leakage beyond the RCS makeup capability needed to satisfy Appendix R,Section III.L.2 (NRC Inspection Report 50-395/01-10).
increased seal leakage beyond the RCS makeup capability needed to satisfy Appendix R,
Section III.L.2 (NRC Inspection Report 50-395/01-10).


==DISCUSSION==
==DISCUSSION==
The NRC uses "deterministic" information to determine the existence of performancedeficiencies. The risk significance of an identified performance deficiency is evaluated using
The NRC uses deterministic information to determine the existence of performance
 
deficiencies. The risk significance of an identified performance deficiency is evaluated using
 
probabilistic risk assessment (PRA) models.
 
In each case cited above, the NRC inspectors attributed the performance deficiency to


probabilistic risk assessment (PRA) models.In each case cited above, the NRC inspectors attributed the performance deficiency toinconsistent recovery procedures. They observed that the plant emergency procedures for a
inconsistent recovery procedures. They observed that the plant emergency procedures for a


loss of all AC power did not agree with the plant procedures for mitigating the effects of a
loss of all AC power did not agree with the plant procedures for mitigating the effects of a


postulated fire. The post-fire procedures failed to direct plant personnel to restore RCP seal
postulated fire. The post-fire procedures failed to direct plant personnel to restore RCP seal


cooling before the seal temperature exceeds the vendor-specified limit. The inspection findings
cooling before the seal temperature exceeds the vendor-specified limit. The inspection findings


from Turkey Point also indicate that the fire mitigation procedures fail to consider that
from Turkey Point also indicate that the fire mitigation procedures fail to consider that


restoration of seal cooling is a time-critical operator action. For seal packages in general, the makeup capability must exceed the seal leakoff to ensurethat a hot standby condition can be achieved (according to the requirements in Appendix R,
restoration of seal cooling is a time-critical operator action. For seal packages in general, the makeup capability must exceed the seal leakoff to ensure
Section III. L.1. (c) and that the pressurizer level is maintained in the indicating range(according to the performance goals in Appendix R, Section III L.2.b).  Furthermore, protectingseal integrity would be assisted if procedures for operating equipment needed for post-fire
 
that a hot standby condition can be achieved (according to the requirements in Appendix R,
Section III. L.1. (c) and that the pressurizer level is maintained in the indicating range


shutdown are consistent with vendor recommendations. For the Westinghouse RCP seals, as
(according to the performance goals in Appendix R, Section III L.2.b). Furthermore, protecting
 
seal integrity would be assisted if procedures for operating equipment needed for post-fire
 
shutdown are consistent with vendor recommendations. For the Westinghouse RCP seals, as


discussed in a recently submitted document on RCP seal performance (Reference 3), a
discussed in a recently submitted document on RCP seal performance (Reference 3), a


leakage rate of 21 gpm per RCP may be assumed in the licensee's safe shutdown assessment
leakage rate of 21 gpm per RCP may be assumed in the licensees safe shutdown assessment


following the loss of all RCP seal cooling. Assumed leakage rates greater than 21 gpm are
following the loss of all RCP seal cooling. Assumed leakage rates greater than 21 gpm are


only warranted if increased seal leakage is postulated as a result of deviations from seal vendor
only warranted if increased seal leakage is postulated as a result of deviations from seal vendor


recommendations. Test or operating experience may be used to justify other RCP seal leakage
recommendations. Test or operating experience may be used to justify other RCP seal leakage
 
rates.
 
Licensees with Westinghouse RCP seals have developed fire emergency procedures to cope


rates.Licensees with Westinghouse RCP seals have developed fire emergency procedures to copewith a loss of all RCP seal cooling by either reestablishing seal cooling to the RCPs before
with a loss of all RCP seal cooling by either reestablishing seal cooling to the RCPs before


increased seal leakage occurs (to prevent increased leakage) or by providing sufficient RCS
increased seal leakage occurs (to prevent increased leakage) or by providing sufficient RCS


makeup to achieve and maintain post-fire safe shutdown.Performance deficiencies and violations of regulatory requirements can result from all of thefollowing: (1) procedural deviations from the manufacturer's recommendations without a
makeup to achieve and maintain post-fire safe shutdown.
 
Performance deficiencies and violations of regulatory requirements can result from all of the
 
following: (1) procedural deviations from the manufacturers recommendations without a
 
documented basis, (2) inadequate procedures, and (3) inadequate documented analysis to
 
show that Appendix R, Section III.L requirements are met.
 
If a performance deficiency exists, it is evaluated in the significance determination process


documented basis, (2) inadequate procedures, and  (3) inadequate documented analysis to
(SDP) using PRA models. The loss of RCP seal cooling has been extensively modeled in PRA


show that Appendix R, Section III.L requirements are met.If a performance deficiency exists, it is evaluated in the significance determination process(SDP) using PRA models.  The loss of RCP seal cooling has been extensively modeled in PRA
applications. In particular, the NRC used PRA information from its closure of a generic safety


applications.  In particular, the NRC used PRA information from its closure of a generic safetyissue involving RCP seal failure (Reference 1) and from its safety evaluation of an industry
issue involving RCP seal failure (Reference 1) and from its safety evaluation of an industry


model of RCP seal leakage (Reference 2) as the SDP framework to evaluate the risk
model of RCP seal leakage (Reference 2) as the SDP framework to evaluate the risk


significance of certain fire protection inspection findings. In the Surry case, the NRC estimated
significance of certain fire protection inspection findings. In the Surry case, the NRC estimated


that the increase in the core damage frequency was between 1E-6 and 1E-5 per year (a white
that the increase in the core damage frequency was between 1E-6 and 1E-5 per year (a white


inspection finding). This finding is highly dependent on the plant-specific electrical switchgear
inspection finding). This finding is highly dependent on the plant-specific electrical switchgear
 
room arrangement and the fire mitigation strategy.
 
In the recently submitted document on RCP seal performance (Reference 3), the NRC has not
 
found sufficient new information to improve PRA models from previously issued industry models
 
(Reference 4) or safety evaluation reports (Reference 2).
 
The PRA modeling considers two cases. In case 1 (plants with Westinghouse high- temperature O-rings and seals), Westinghouse, the RCP seal vendor, states that after loss of


room arrangement and the fire mitigation strategy.In the recently submitted document on RCP seal performance (Reference 3), the NRC has notfound sufficient new information to improve PRA models from previously issued industry models
seal cooling, the seals with high-temperature O-rings will leak at about 21 gpm per pump. If the


(Reference 4) or safety evaluation reports (Reference 2).The PRA modeling considers two cases.  In case 1 (plants with Westinghouse high-temperature O-rings and seals), Westinghouse, the RCP seal vendor, states that after loss ofseal cooling, the seals with high-temperature O-rings will leak at about 21 gpm per pump.  If thelicensee implements vendor guidelines, this condition is not expected to proceed to failures
licensee implements vendor guidelines, this condition is not expected to proceed to failures


resulting in leak rates greater than 21 gpm per pump. Even if seal cooling is not reestablished, degradation of the seals for leakage rate to significantly increase is not expected for an indefinite period of time if the RCPs are secured before the seal temperature exceeds 235degrees F. Restoration of seal cooling may result in cold thermal shock of the seal and
resulting in leak rates greater than 21 gpm per pump. Even if seal cooling is not reestablished, degradation of the seals for leakage rate to significantly increase is not expected for an indefinite period of time if the RCPs are secured before the seal temperature exceeds 235 degrees F. Restoration of seal cooling may result in cold thermal shock of the seal and


possibly cause increased seal leakage. If seal cooling is restored using component cooling
possibly cause increased seal leakage. If seal cooling is restored using component cooling


water (CCW) to the thermal barrier cooler, water hammer may occur and possibly compromise
water (CCW) to the thermal barrier cooler, water hammer may occur and possibly compromise


the integrity of the CCW system. As discussed in the recently submitted document on RCPseal performance (Reference 3), if the CCW system is damaged, then plant shutdown after afire accident may not be possible in all scenarios.To be consistent with 10 CFR Part 50, Appendix B, "Quality Assurance Criteria for NuclearPower Plants and Fuel Reprocessing Plants," protection of seal integrity depends on fire
the integrity of the CCW system. As discussed in the recently submitted document on RCP
 
seal performance (Reference 3), if the CCW system is damaged, then plant shutdown after a
 
fire accident may not be possible in all scenarios.
 
To be consistent with 10 CFR Part 50, Appendix B, Quality Assurance Criteria for Nuclear
 
Power Plants and Fuel Reprocessing Plants, protection of seal integrity depends on fire
 
protection and RCP recovery procedures being consistent with the manufacturers
 
recommendations and that the associated instrumentation, alarms, and recovery procedures
 
are available after a fire.
 
In case 1 (plants with Westinghouse high-temperature O-rings and seals), the NRC PRA
 
modeling accounts for two failure scenarios, given a loss of seal cooling with no RCPs
 
operating. In failure scenario 1 (hot shock), during initial heating of the seals, hydraulic
 
instability caused by fluid flashing can potentially open (pop) the second-stage seal faces


protection and RCP recovery procedures being consistent with the manufacturer's
(Reference 2). For this scenario, the NRC PRA model assumes that the popping failure of the


recommendations and that the associated instrumentation, alarms, and recovery proceduresare available after a fire.In case 1 (plants with Westinghouse high-temperature O-rings and seals), the NRC PRAmodeling accounts for two failure scenarios, given a loss of seal cooling with no RCPs
second-stage seal occurs at 13 minutes after loss of RCP seal cooling.


operating.  In failure scenario 1 (hot shock), during initial heating of the seals, hydraulic
In case 1, failure scenario 2 (cold shock), if RCP seal cooling is restored after the seal


instability caused by fluid flashing can potentially open (pop) the second-stage seal faces(Reference 2).  For this scenario, the NRC PRA model assumes that the popping failure of thesecond-stage seal occurs at 13 minutes after loss of RCP seal cooling.In case 1, failure scenario 2 (cold shock), if RCP seal cooling is restored after the sealtemperature exceeds the vendor-specified limit, given survival from the initial hot shock of the
temperature exceeds the vendor-specified limit, given survival from the initial hot shock of the


seals, the NRC uses seal failure pr
seals, the NRC uses seal failure probabilities and consequential seal leakage sizes similar to


obabilities and consequential seal leakage sizes similar tothose used in failure scenario 1.In case 2 of the NRC PRA model (Westinghouse plants with "old," pre-high-temperature RCPseals), Westinghouse, the RCP seal vendor, states that after loss of seal cooling, the "old"seals could fail after about 30 minutes.  Therefore, protection of seal integrity requires the
those used in failure scenario 1.


restoration of seal cooling within the appropriate time limit.  However, this time limit is
In case 2 of the NRC PRA model (Westinghouse plants with old, pre-high-temperature RCP


approximate. Plant-specific vendor guidance may differ based on (1) commitments made with
seals), Westinghouse, the RCP seal vendor, states that after loss of seal cooling, the old
 
seals could fail after about 30 minutes. Therefore, protection of seal integrity requires the
 
restoration of seal cooling within the appropriate time limit. However, this time limit is
 
approximate. Plant-specific vendor guidance may differ based on (1) commitments made with


respect to the station blackout analysis and (2) licensee-specific vendor recommendations.
respect to the station blackout analysis and (2) licensee-specific vendor recommendations.


==CONTACT==
==CONTACT==
This information notice requires no specific action or written response. Please direct anyquestions about this matter to the technical contact(s) listed below or the appropriate
This information notice requires no specific action or written response. Please direct any
 
questions about this matter to the technical contact(s) listed below or the appropriate NRR
 
project manager.


NRR project manager./RA/Patrick L. Hiland, Chief
/RA/
                                            Patrick L. Hiland, Chief
 
Reactor Operations Branch


===Reactor Operations Branch===
Division of Inspection Program Management
Division of Inspection Program Management


Office of Nuclear Reactor RegulationTechnical Contacts:Phil Qualls, NRRMichael Franovich, NRR301-415-1849301-415-3361 E-mail: pmq@nrc.govE-mail: mxf1@nrc.govAlbert Wong, NMSS301-415-7843 E-mail: axw2@nrc.govAttachment:  ReferencesNote: NRC generic communications may be found on the
Office of Nuclear Reactor Regulation
 
Technical Contacts: Phil Qualls, NRR                Michael Franovich, NRR
 
301-415-1849                  301-415-3361 E-mail: pmq@nrc.gov            E-mail: mxf1@nrc.gov
 
Albert Wong, NMSS
 
301-415-7843 E-mail: axw2@nrc.gov


NRC public Web site,http://www.nrc.gov, under Electronic Reading Room/Document Collections.
Attachment: References
 
Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, under Electronic Reading Room/Document Collections.


==CONTACT==
==CONTACT==
This information notice requires no specific action or written response. Please direct anyquestions about this matter to the technical contact(s) listed below or the appropriate
This information notice requires no specific action or written response. Please direct any
 
questions about this matter to the technical contact(s) listed below or the appropriate NRR
 
project manager.
 
/RA/
                                            Patrick L. Hiland, Chief


NRR project manager./RA/Patrick L. Hiland, Chief
Reactor Operations Branch


===Reactor Operations Branch===
Division of Inspection Program Management
Division of Inspection Program Management


Office of Nuclear Reactor RegulationTechnical Contacts:Phil Qualls, NRRMichael Franovich, NRR301-415-1849301-415-3361 E-mail: pmq@nrc.govE-mail: mxf1@nrc.govAlbert Wong, NMSS301-415-7843 E-mail: axw2@nrc.govAttachment: ReferencesNote: NRC generic communications may be found on the
Office of Nuclear Reactor Regulation
 
Technical Contacts: Phil Qualls, NRR                  Michael Franovich, NRR
 
301-415-1849                    301-415-3361 E-mail: pmq@nrc.gov            E-mail: mxf1@nrc.gov
 
Albert Wong, NMSS
 
301-415-7843 E-mail: axw2@nrc.gov
 
Attachment: References
 
Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, under Electronic Reading Room/Document Collections.
 
DISTRIBUTION:
ADAMS
 
IN File
 
ADAMS ACCESSION #: ML051080499 DOCUMENT NAME: E:\Filenet\ML051080499.wpd
 
OFFICE  DSSA:SPLB        Tech Editor    DSSA:SPLB          ADPT:DLPM          ADPT:DLPM
 
NAME    CVHodge          PKleene        SWeerakkody        CGratton            EABrown
 
DATE    05/12/2005      04/06/2005      04/08/2005        05/12/2005          05/16/2005 OFFICE  ADPT:DIPM      ADPT:DIPM        ADPT:DIPM        A:SC:OES:IROB:DIPM  C:IROB:DIPM
 
NAME    SRMonarque      KRCotton          GSShukla          EJBenner            PLHiland
 
DATE    05/12/2005      05/12/2005        05/12/2005        05/16/2005          06/01/2005 OFFICIAL RECORD COPY Attachment
 
REFERENCES


NRC public Web site,http://www.nrc.gov, under Electronic Reading Room/Document Collections.DISTRIBUTION
1.  NRC Regulatory Information Summary 2000-002, Closure of Generic Safety Issue 23, Reactor Coolant Pump Seal Failure, February 15, 2000 (ADAMS ML003680402)
2. NRC Office of Nuclear Reactor Regulation, Safety Evaluation of WCAP-15603, Revision 1, WOG 2000 Reactor Coolant Pump Seal Leakage Model for Westinghouse


:ADAMS
PWRs, Westinghouse Owners Group Project No. 694, May 2003 (ADAMS


IN FileADAMS ACCESSION #: ML051080499DOCUMENT NAME:  E:\Filenet\ML051080499.wpdOFFICEDSSA:SPLBTech EditorDSSA:SPLBADPT:DLPMADPT:DLPMNAMECVHodgePKleeneSWeerakkodyCGrattonEABrownDATE05/12/200504/06/200504/08/200505/12/200505/16/2005OFFICEADPT:DIPMADPT:DIPMADPT:DIPMA:SC:OES:IROB:DIPMC:IROB:DIPMNAMESRMonarqueKRCottonGSShuklaEJBennerPLHilandDATE05/12/200505/12/200505/12/200505/16/200506/01/2005OFFICIAL RECORD COPY AttachmentREFERENCES1.NRC Regulatory Information Summary 2000-002, "Closure of Generic Safety Issue 23,Reactor Coolant Pump Seal Failure," February 15, 2000 (ADAMS ML003680402)2.NRC Office of Nuclear Reactor Regulation, "Safety Evaluation of WCAP-15603,Revision 1, WOG 2000 Reactor Coolant Pump Seal Leakage Model for Westinghouse
ML0314003760)
3. Westinghouse Owners Group, Reactor Coolant Pump Seal Performance for Appendix R


PWRs," Westinghouse Owners Group Project No. 694, May 2003 (ADAMS
Assessments, WCAP-16396-NP, Revision 0, January 2005 (ADAMS ML050320187)
4.  Westinghouse Electric Company, LLC, WOG 2000 Reactor Coolant Pump Seal Leakage


ML0314003760)3.Westinghouse Owners Group, "Reactor Coolant Pump Seal Performance for Appendix RAssessments," WCAP-16396-NP, Revision 0, January 2005 (ADAMS ML050320187)4.Westinghouse Electric Company, LLC, "WOG 2000 Reactor Coolant Pump Seal LeakageModel for Westinghouse PWRs," WCAP-15603, Revision 1, May 2002 (ADAMS
Model for Westinghouse PWRs, WCAP-15603, Revision 1, May 2002 (ADAMS


ML021500485)}}
ML021500485)}}


{{Information notice-Nav}}
{{Information notice-Nav}}

Revision as of 00:29, 24 November 2019

Fire Protection Findings on Loss of Seal Cooling to Westinghouse Reactor Coolant Pumps
ML051080499
Person / Time
Issue date: 06/01/2005
From: Hiland P
NRC/NRR/DIPM/IROB
To:
Franovich M, NRR/DSSA/SPSB, 415-3361
References
IN-05-014
Download: ML051080499 (7)
v • d • e


UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555-0001 June 1, 2005 NRC INFORMATION NOTICE 2005-14: FIRE PROTECTION FINDINGS ON LOSS OF

SEAL COOLING TO WESTINGHOUSE

REACTOR COOLANT PUMPS

ADDRESSEES

All holders of operating licenses for pressurized water reactors, except those who have

permanently ceased operations and have certified that fuel has been permanently removed

from the reactor vessel.

PURPOSE

The U.S. Nuclear Regulatory Commission is issuing this information notice (IN) to inform

addressees about recent inspection findings on post-fire procedural requirements related to

loss of cooling to reactor coolant pump (RCP) seals. NRC anticipates that recipients will review

the information for applicability to their facilities and consider taking actions, as appropriate, to

avoid similar issues. However, no specific action or written response is required.

BACKGROUND

Assuming a fire results in loss of cooling to the RCP seals, licensees may comply with 10 CFR

Part 50, Appendix R, Fire Protection Program for Nuclear Power Facilities Operating Prior to

January 1, 1979, by protecting the cooling to the seals or by demonstrating that the plant can

cope with RCP seal leakoff flow rates. Many licensees have installed RCP seal packages using

high-temperature O-rings that will not result in uncontrolled leakage from RCP seals for

conditions with loss of all RCP seal cooling. Licensees also ensure adequate makeup

capability to compensate for any RCP seal leakoff and maintain reactor coolant system (RCS)

inventory according to requirements of Appendix R, Sections III.G.2, III.G.3, and III.L.1 and

performance goals of Appendix R,Section III.L.2. Note that a plant licensed before January 1,

1979, must meet the provisions of Appendix R,Section III.G and III.L and a plant licensed after

January 1, 1979, must implement the fire protection provisions of its operating license.

DESCRIPTION OF CIRCUMSTANCES

At Surry, NRC inspectors found that certain postulated fires could result in the loss of cooling to

the RCP seals. The inspectors noted that the RCP seal vendor, Westinghouse, advised that

increased seal leakage, to around 21 gpm, could occur if seal cooling is lost and not restored

before hot RCS fluid reaches the RCP seals. Additionally, the Westinghouse Owners Group

(WOG) revised their generic emergency response guidelines for the station blackout event to

recommend that RCP seal cooling not be restored following a prolonged loss of seal cooling in

which the seal temperature exceeds the RCP seal vendors recommendations. The licensee

incorporated this guidance into its emergency operating procedures for the response to a loss

of all alternating current (AC) power event but not in its procedures for safe shutdown of the

reactor after a fire. Restoration of seal injection after the seals become hot could lead to

increased leakage beyond the RCS makeup capability needed to satisfy the performance goals

in Appendix R,Section III.L.2 (NRC Inspection Reports 50-280/03-07 and 50-281/03-07).

Similar findings were made at other nuclear power plants. At Turkey Point, NRC inspectors

found that the post-fire procedures did not provide timely operator action to restore seal

injection and could result in increased RCP seal leakage beyond the capacity of equipment

dedicated to achieve and maintain post-fire safe shutdown according to Appendix R, Section

III.G.2 (NRC Inspection Reports 50-250/04-07 and 50-251/04-07). At North Anna, NRC

inspectors found, similar to the Surry finding, that certain fires could result in a loss of seal

cooling. Seal cooling could be restored after the seal had heated up, thereby potentially

resulting in increased seal leakage beyond the RCS makeup capability required to satisfy

Appendix R,Section III.L.2 (NRC Inspection Reports 50-338/03-06 and 50-339/03-06). At

Summer, the inspectors were concerned that the licensees fire emergency procedure did not

direct personnel to reestablish seal cooling flow in a timely manner, potentially leading to

increased seal leakage beyond the RCS makeup capability needed to satisfy Appendix R,

Section III.L.2 (NRC Inspection Report 50-395/01-10).

DISCUSSION

The NRC uses deterministic information to determine the existence of performance

deficiencies. The risk significance of an identified performance deficiency is evaluated using

probabilistic risk assessment (PRA) models.

In each case cited above, the NRC inspectors attributed the performance deficiency to

inconsistent recovery procedures. They observed that the plant emergency procedures for a

loss of all AC power did not agree with the plant procedures for mitigating the effects of a

postulated fire. The post-fire procedures failed to direct plant personnel to restore RCP seal

cooling before the seal temperature exceeds the vendor-specified limit. The inspection findings

from Turkey Point also indicate that the fire mitigation procedures fail to consider that

restoration of seal cooling is a time-critical operator action. For seal packages in general, the makeup capability must exceed the seal leakoff to ensure

that a hot standby condition can be achieved (according to the requirements in Appendix R,

Section III. L.1. (c) and that the pressurizer level is maintained in the indicating range

(according to the performance goals in Appendix R,Section III L.2.b). Furthermore, protecting

seal integrity would be assisted if procedures for operating equipment needed for post-fire

shutdown are consistent with vendor recommendations. For the Westinghouse RCP seals, as

discussed in a recently submitted document on RCP seal performance (Reference 3), a

leakage rate of 21 gpm per RCP may be assumed in the licensees safe shutdown assessment

following the loss of all RCP seal cooling. Assumed leakage rates greater than 21 gpm are

only warranted if increased seal leakage is postulated as a result of deviations from seal vendor

recommendations. Test or operating experience may be used to justify other RCP seal leakage

rates.

Licensees with Westinghouse RCP seals have developed fire emergency procedures to cope

with a loss of all RCP seal cooling by either reestablishing seal cooling to the RCPs before

increased seal leakage occurs (to prevent increased leakage) or by providing sufficient RCS

makeup to achieve and maintain post-fire safe shutdown.

Performance deficiencies and violations of regulatory requirements can result from all of the

following: (1) procedural deviations from the manufacturers recommendations without a

documented basis, (2) inadequate procedures, and (3) inadequate documented analysis to

show that Appendix R,Section III.L requirements are met.

If a performance deficiency exists, it is evaluated in the significance determination process

(SDP) using PRA models. The loss of RCP seal cooling has been extensively modeled in PRA

applications. In particular, the NRC used PRA information from its closure of a generic safety

issue involving RCP seal failure (Reference 1) and from its safety evaluation of an industry

model of RCP seal leakage (Reference 2) as the SDP framework to evaluate the risk

significance of certain fire protection inspection findings. In the Surry case, the NRC estimated

that the increase in the core damage frequency was between 1E-6 and 1E-5 per year (a white

inspection finding). This finding is highly dependent on the plant-specific electrical switchgear

room arrangement and the fire mitigation strategy.

In the recently submitted document on RCP seal performance (Reference 3), the NRC has not

found sufficient new information to improve PRA models from previously issued industry models

(Reference 4) or safety evaluation reports (Reference 2).

The PRA modeling considers two cases. In case 1 (plants with Westinghouse high- temperature O-rings and seals), Westinghouse, the RCP seal vendor, states that after loss of

seal cooling, the seals with high-temperature O-rings will leak at about 21 gpm per pump. If the

licensee implements vendor guidelines, this condition is not expected to proceed to failures

resulting in leak rates greater than 21 gpm per pump. Even if seal cooling is not reestablished, degradation of the seals for leakage rate to significantly increase is not expected for an indefinite period of time if the RCPs are secured before the seal temperature exceeds 235 degrees F. Restoration of seal cooling may result in cold thermal shock of the seal and

possibly cause increased seal leakage. If seal cooling is restored using component cooling

water (CCW) to the thermal barrier cooler, water hammer may occur and possibly compromise

the integrity of the CCW system. As discussed in the recently submitted document on RCP

seal performance (Reference 3), if the CCW system is damaged, then plant shutdown after a

fire accident may not be possible in all scenarios.

To be consistent with 10 CFR Part 50, Appendix B, Quality Assurance Criteria for Nuclear

Power Plants and Fuel Reprocessing Plants, protection of seal integrity depends on fire

protection and RCP recovery procedures being consistent with the manufacturers

recommendations and that the associated instrumentation, alarms, and recovery procedures

are available after a fire.

In case 1 (plants with Westinghouse high-temperature O-rings and seals), the NRC PRA

modeling accounts for two failure scenarios, given a loss of seal cooling with no RCPs

operating. In failure scenario 1 (hot shock), during initial heating of the seals, hydraulic

instability caused by fluid flashing can potentially open (pop) the second-stage seal faces

(Reference 2). For this scenario, the NRC PRA model assumes that the popping failure of the

second-stage seal occurs at 13 minutes after loss of RCP seal cooling.

In case 1, failure scenario 2 (cold shock), if RCP seal cooling is restored after the seal

temperature exceeds the vendor-specified limit, given survival from the initial hot shock of the

seals, the NRC uses seal failure probabilities and consequential seal leakage sizes similar to

those used in failure scenario 1.

In case 2 of the NRC PRA model (Westinghouse plants with old, pre-high-temperature RCP

seals), Westinghouse, the RCP seal vendor, states that after loss of seal cooling, the old

seals could fail after about 30 minutes. Therefore, protection of seal integrity requires the

restoration of seal cooling within the appropriate time limit. However, this time limit is

approximate. Plant-specific vendor guidance may differ based on (1) commitments made with

respect to the station blackout analysis and (2) licensee-specific vendor recommendations.

CONTACT

This information notice requires no specific action or written response. Please direct any

questions about this matter to the technical contact(s) listed below or the appropriate NRR

project manager.

/RA/

Patrick L. Hiland, Chief

Reactor Operations Branch

Division of Inspection Program Management

Office of Nuclear Reactor Regulation

Technical Contacts: Phil Qualls, NRR Michael Franovich, NRR

301-415-1849 301-415-3361 E-mail: pmq@nrc.gov E-mail: mxf1@nrc.gov

Albert Wong, NMSS

301-415-7843 E-mail: axw2@nrc.gov

Attachment: References

Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, under Electronic Reading Room/Document Collections.

CONTACT

This information notice requires no specific action or written response. Please direct any

questions about this matter to the technical contact(s) listed below or the appropriate NRR

project manager.

/RA/

Patrick L. Hiland, Chief

Reactor Operations Branch

Division of Inspection Program Management

Office of Nuclear Reactor Regulation

Technical Contacts: Phil Qualls, NRR Michael Franovich, NRR

301-415-1849 301-415-3361 E-mail: pmq@nrc.gov E-mail: mxf1@nrc.gov

Albert Wong, NMSS

301-415-7843 E-mail: axw2@nrc.gov

Attachment: References

Note: NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov, under Electronic Reading Room/Document Collections.

DISTRIBUTION:

ADAMS

IN File

ADAMS ACCESSION #: ML051080499 DOCUMENT NAME: E:\Filenet\ML051080499.wpd

OFFICE DSSA:SPLB Tech Editor DSSA:SPLB ADPT:DLPM ADPT:DLPM

NAME CVHodge PKleene SWeerakkody CGratton EABrown

DATE 05/12/2005 04/06/2005 04/08/2005 05/12/2005 05/16/2005 OFFICE ADPT:DIPM ADPT:DIPM ADPT:DIPM A:SC:OES:IROB:DIPM C:IROB:DIPM

NAME SRMonarque KRCotton GSShukla EJBenner PLHiland

DATE 05/12/2005 05/12/2005 05/12/2005 05/16/2005 06/01/2005 OFFICIAL RECORD COPY Attachment

REFERENCES

1. NRC Regulatory Information Summary 2000-002, Closure of Generic Safety Issue 23, Reactor Coolant Pump Seal Failure, February 15, 2000 (ADAMS ML003680402)

2. NRC Office of Nuclear Reactor Regulation, Safety Evaluation of WCAP-15603, Revision 1, WOG 2000 Reactor Coolant Pump Seal Leakage Model for Westinghouse

PWRs, Westinghouse Owners Group Project No. 694, May 2003 (ADAMS

ML0314003760)

3. Westinghouse Owners Group, Reactor Coolant Pump Seal Performance for Appendix R

Assessments, WCAP-16396-NP, Revision 0, January 2005 (ADAMS ML050320187)

4. Westinghouse Electric Company, LLC, WOG 2000 Reactor Coolant Pump Seal Leakage

Model for Westinghouse PWRs, WCAP-15603, Revision 1, May 2002 (ADAMS

ML021500485)


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